Process of manufacturing artificial stone.



UNITED STATES PATENT ornron.

Application filed .3

Specification of Letters Patent.

Patented Aug. 22, 1905.

Serial No. 219,369-

To aZZ whom, it party concern:

Be it known that I, JAooB STAUDT, chemist, a subject of the GermanEmperor, residing at 64: Arndtstrasse, Bonn, Germany, have inventedcertain new and useful Im provementsin Processes of ManufacturingArtificial Stone, of which the following is a specification.

This invention relates to a process for man ufacturing artificial stone,of which the following is a specilication.

Hitherto a process has been known for manufacturing artificial stone inwhich a mixture of sand and chalk, to which twenty-five per cent. oflinseed-oil varnish has been added, is pressed into molds and dried foreight days at a temperature of 100 to 150 centigrade.

In spite of the extremely long duration of the drying and hardeningperiod of the process referred to stones or blocks of but moderatehardness and inconsiderablestrength and toughness result from itsemployment and because of the character of the drying operation (whichreally consists in the hardening of the cementing medium from withoutinward) stones or blocks of but small sizes can be produced and onlysuch cementing mediums can be used as harden readily-as, for instance,the fatty varnishes. To reduce the duration of the drying period to anyconsiderable extent in this prior process by increasing the dryingtempcrature results merelyin giving to the stones or blocks a hardexterior crust, while within they remain soft. This exterior crust (moreespecially when a high proportion of the binding medium is used)presents a rough and blistered appearance and the stones or blocksthemselves lose their shape and become distorted. The higher thetemperature employed the more accentuated become the inherentdifficulties referred to. If, however, the duration of the drying periodin that process is reduced to a considerable extent, 'then the stonesreceive a hard crust outside while remaining soft inside. The outsidecrust. more particularly when a high proportion of binding medium isused, appears rough and blistery, while the stones themselves lose theirshape and become distorted. If, on the other hand, still highertemperatures are employed, 7

the drawbacks in question become accentuated and no better result isattained as regards the hardening.

This invention relates to a process by means of which it is possible toproduce such artificial stone of much greater hardness, strength, andtoughness in a considerably shorter time without the disadvantageshereinbefore mentioned. The process, moreover, permits the manufactureof stones of larger size, as well as the use of all those oily and fattycementing mediums which have the property of becoming converted intoahard mass when exposed in the form of thin layers to the action of airand heat as the result of a chemical reaction. These are preferablythose fats and oils, as well as their varnishes, which consist of themore or less complex compounds of glycerids of fatty acids, and alsocompounds of fatty acids of the group of animal and vegetable waxesrelated to the fats, and finally the heavy rosinoils.

The process consists in commencing the chemical reactions which resultin the bardening of the cementing substances before the molding andcarrying them out to such an extent as is permitted by the necessity ofkeeping the mixture in a plastic state. This is effected by exposing themixed materials, which consist of the binding substances and the fillingsubstances ground more or less finely and which constitute a moistpowder, to the action of air at a suitable temperature, the loosepowdery nature of the said mass facilitating the commencement and thecontinuance of the chemical processes which take place.

This process differs considerably from the well-known stiffening ofoil-putty or cement by simply leaving about masses kneaded into hardcakes. In that case the outer crust sets into a crumbly mass, theinterior remaining unaffected. By repeated kneading it is possible, itis true, to attain a slight stiffening, but it never can be verythorough, as a large proportion 'of the set crust would affect thecohesion of the cement or binding medium. Another method of stiffeningcement is based. on the chemical reaction between suitablyselectedfilling materials and the cements. This reaction between solid andviscous substances takes place, however, in such an extraordinarily slowmanner that the stiffening in question necessitates leaving the materialfor days and weeks, while by the process of this invention a fairlythorough stiffening can be obtained in a few hours. In this way it ispossible to prepare the mixture of materials Without affecting theirplasticity for final hardening after the molding in such a way that evenin the case of large stones when sufficient heat is used the saidhardening takes. place uniformly throughout the whole of the mass intwelve to twenty-four hours, and the products thus obtained, in spite ofthe short time of manufacturing, are distinguished by great hardness,strength, and toughness. The character of the chemical reactions whichtake place in the cement during the hardening process is not yet fullyascertained. It is probable that oxidation plays a prominent part inwhat occurs and that such new com pounds as are produced thereby areagain partially disassociated and volatilized. For all practicalpurposes the resultant gradual conversion of the cement from the liquidinto the solid state may be appropriately designated as a stiffening ofthe mixture.

When the so-called siccative oils are used as cementsuoh as, forinstance, linseed-oil and its varnisheswhen they are not added inexcessive quantities this stiffening process can be started attheordinary room temperature to centigrade) and is then completed in twelveto twenty-four hours. By using suitable higher temperatures the processis considerably accelerated, even when large quantities of cementareadded. When the socalled non-siccative oils are used, as well asconsistent fats and waxes, the stiffening should preferably be effectedafter a more or less considerable heating. The temperature and timesuitable for stiffening differ for different kinds of cements and mustbe determined by experiment for each individual case. The following, forinstance, have been ascertained: linseed-oil varnish, to centigrade andtwo to three hours; raw linseed-oil, 80 to centigrade and three to fourhours; rapeseed oil, 90 to centigrade and four to five hours;blubber-oil, 100 to centigrade and five to six hours; tallow, 110 tocentigrade and six to seven hours; palmoil, 120 to 14:0 centigrade andseven to eight hours.

As already stated, the stiffening process must be interrupted below acertain limit in order that the plasticity of the mixture may bepreserved. As will be seen from the examples given above, this limit isreached for different cements at difierent periods of time and atdifferent temperatures. Generally speaking, the proper moment can berecognized by a pungent smell becoming noticeable in the mixtures. Thenthe process must be stopped; otherwise the cement would become partlydecomposed and the mixtures would lose their plasticity and soon passinto a hard sandy state. The time required for stifiening the mixturemaybe reduced considerably by increasing the stiffening temperaturesbeyond those stated in the foregoing-specific instances, the necessaryprecautions being taken to prevent burning. Forexample, mixtures offilling substances and Well-hardening oils may be stiffened Withinfifteen to twenty minutes when heated to a temperature from 14:0 tocentigrade. In fact the duration of the stiffening operation may beconsiderably reduced in any of the instances mentioned. As soon as theproper degree of stiffening has been reached the mixtures, either in thehot or in the cooled state, form loose powdery masses, which no longerfeel moist to the touch, but which can still be easily formed intobodies by pressure. Solid fats behave in exactly the same way as oils,and mixtures prepared with them do not get solid on being cooled. ,Themixtures can therefore be treated both in a hot and in a cooled state,and there is no need to fear that a reduction of temperature during themolding will be disadvantageous. As cold material is easier to treatthan hot, it is even advisable to cool the mixtures down to a certaindegree.

Solid fats and waxes are melted before being mixed with fillingsubstances and the latter correspondingly heated. As the stiffeningtemperatures of solid fats and waxes are beyond their melting-point,they can be considered before the stiffening as liquids and as behavingin exactly the same manner as oils.

By strongly boiling the so-called siccative. oils with or withoutaddition of certain chemicals varnishes are produced, as is well known,which are more or less viscous and can be considered as cements whichhave already been stiffened to a certain extent independently of thefilling materials. According to their nature these varnishes, in orderto enable them to be mixed with filling material, must be more or lessdiluted. To that end very thin fluid additions are used, which whenheated evaporate again before the proper stifiening process of thecement in combination with the filling material has been completed tothe desired degree.

As filling material for the process of this invention can be usedvarious raw materials ground more or less finely that is to say,generally speaking, all substances which can be ground sufficiently fineor occur in a sufficiently fine state, as long as they are not, or

only with difficulty, soluble in water and as long as they do notundergo such modification as to make the molding of the stiffened powderimpossible and are capable of withstanding the temperature required forhardening.

The proportion of cement in the case of very high pressure being usedfor molding can be made very small,(down to five per cent;) but withsufliciently long stiffening it can be raised to twenty per cent. andmore. It is, however, not necessary to have such a high proportion ofcement, as stones of great hardness and resistance to water can beobtained at a medium pressure with a proportion of cement equal to tento fifteen per cent., by

volume, if suitable temperatures be used. The temperatures, however,which must be used after the molding for completing the hardening of thestones differ to a certain expatterns may be produced.

tentwith the different cements, but notwithin I agitating the mixture bymeans of a small such wide limits as the stiffening temperatures.

At a temperature of to centigrade the stones are already, it is true,fairly tough, but still of but moderate hardness and absorb water at thebreaking joints. The socalled siccative oils and their varnishes givevery good results at temperatures varying between 120 and centigrade,while other oils require a slightly higher and solid fats still higherhardening temperature. Generally speaking, the best results are obtainedwith temperatures of about to 180 centigrade; but the stiffeningtemperature and the duration of stiffening depend not only on the kind,but also on the quantity of cement and also on the nature of the fillingused, so that the temperatures stated above must be varied to a greateror less extent in accordance with the circumstances of each individualcase. As, generally speaking, the duration of the stiffening process isthe shorter the higher the temperature, the temperature can often beconsiderably raised, all other conditions remaining the same; but thenprecautions must be taken against burning. At very high temperatures,exceeding 200 centigrade, the hardness begins to decrease again untilthe cement is finally destroyed.

The choice of the filling to be used depends on the object for which thestone to be manufactured is to be used. If it is intended to produceinsulating bodies for electrotechnical purposes, then fine quartz-sand,quartz-powder, ground feldspar or lime spar, ground glass, and otherinsulating substances can be used. For manufacturing grinding orpolishing stones it is advisable to use as filling more or less finelyground raw materials used for grinding and polishing purposes, such asemery, carborundum, Viennalime, and the like. If it is desired toproduce colored stones, then it is advisable to mix in a suitableproportion filling substances which affect the coloration little aspossible-as, for in stance, quartz-meal, ground feldspar, lime spar,bright clay, and the like, with the wellknown body-colors such, forinstance, as are used in the cement-plate manufacture. Such mixtures ofcolor can also be put on in a thin layer by pressing on the ground massmainly consisting of screened quartz-sand, and in this waysplendidly-colored plates with beautiful If the stone is to be used forsome other object, then the filling must be selected accordingly.

In accordance with the above description the process may be carried out,say, as follows: In an earthen vessel are mixed one kilogram finequartz-meal, such as is used as addition to the material in themanufacture of pottery, and one half kilogram pure quartz sandpreviously screened through a screen with Sixty-four meshes per inch,while thoroughly metal spade. Thereupon one hundred and fifty grams ofraw commercially pure linseed-oil are poured in, the whole thoroughlyWell stired with a wooden spade, kneaded with the hand in order to makethe mixture more uniform, and rubbed so as to disintegrate any hardlumps that may have formed,and to obtain a loose moist powder,'and themixture is first screened through a sieve of twelve meshes and thenthrough one of twenty-four meshes per inch. Themoist powder is thenspread on a flanged metal plate in a thin layer about one centimeterdeep and brought into the heating-chamber, in which the temperature ismaintained at 85 centigrade by means of hot air. After leaving it therefor two hours the mixture loses its moist nature and the stiffeningprocess is at an end. The metal plate is then removed from theheating-chamber and the mixture cooled. After having rubbed it againthrough a screen with twentyfour meshes per inch in order to loosen anyparticles that may have baked together and to obtain perfect uniformitya final product is obtained in the shape of a dry powder which is nolonger smeary, but which can still be compressed by strong pressure. Thematerial is then filled into molds of a spindle-press, the fly-wheel ofwhich is moved by hand or by power, according to its size, and thepressure is exercised by turning the spindle, whereby a plunger iscaused to descend in the well-known manner. After completing thepressure the stones are ejected from the mold by means of an ejectordevice placed on perforated metal plates and introduced into aheating-chamber. The temperature of the said chamber is raised withinsix hours to centigrade by admitting hot air. This temperature is keptup during six hours, and during the further six hours cooled down tosuch an extent that the stones which at that time are perfectly readyand quite hard can be taken out.

The stiffened powder constitutes a suitable material for manufacturingcomplicated parts by dry pressure, as it can be pressed into the finestoutlines without adhering to the mold when the molded part is taken out.

Stone produced by the process hereinbefore described is distinguished byextraordinary strength, toughness, and resistance to Water, which renderit thoroughly suitable for various purposes. Thus, for instance, byselecting suitable filling it can be used for manufacturing insulatorsfor electrotechnical purposes, for grinding and polishing stones, andthe like.

What 1 claim as my invention, and desire to secure by Letters Patent,is-

1. The herein-described process of making artificial stone, whichconsists in mixing a comminuted filling material with an oxidizablebinding agent in quantity sufficient to produce a moist loose powder,stiffening said powder by exposing it to the action of the air, andthereafter molding the mixture into stone; substantially as described.

2. The herein-described process of making artificial stone, whichconsists in mixing a comminuted filling material with an oxidizablebinding agent in quantity sufficient to produce a moist loose powder,stiffening said powder by exposing it in thin layers to the action ofthe air, and thereafter molding the mixture into stone; substantially asdescribed.

3. The hereindescribed process of making artificial stone, whichconsists in mixing a comminuted filling material with an oily bindingagent in quantity sufficieut to produce a moist loose powder, stiffeningsaid powder by exposing it to the action of the air, and thereaftermolding the mixture into stone; sul stantially as described.

4. The herein-described process of making artificial stone, whichconsists in mixing a refractory insoluble powdery filling substance withfrom five per cent. to twenty per cent. of an oily binding medium so asto produce a moist loose powder, stiffening said powder withoutdestroying its plasticity, and thereafter molding the mixture intostone, the hardening of the stone being accelerated by baking;substantially as described.

5. The herein-described process of making artificial stone, whichconsists in mixing a refractory insoluble powdery filling substance withfrom five per cent. to twenty per cent. of an oily binding medium so asto produce a moist loose powder, stiffening said powder withoutdestroying its plasticity, and thereafter molding the mixture intostone, the hardening of the stone being accelerated by baking at atemperature as high as 200 centigrade for twelve to twenty-four hours;substantially as described.

6. The herein-described process of making artificial stone, whichconsists in mixing powdered quartz-meal and quartz-sand with from fiveper cent. to twenty per cent. of linseedoil, rubbing and screening themixture into the form of a moist loose powder, heating the mixture tostiffen it without destroying its plasticity and thereafter molding themixture into stone. substantially as described.

7. The herein-described process of making artificial stone, whichconsists in mixing powdered quartz-meal and quartz-sand with from fiveper cent. to twenty per cent. of linseedoil, rubbing and screening themixture into the form of a moist loose powder, heating the mixture in athin layer to stiffen it without destroying its plasticity andthereafter molding the mixture into stone, the hardening of the stonebeing accelerated by baking it at a temperature as high as 200centigrade for twelve to twenty-four hours; substantially as described.

In testimon y whereof I have signed my name to this specification inpresence of two witnesses.

JACOB STAUDT.

Witnesses:

\VILLIAM KNEPPERS, J OH. SOHOLZ.

